There's nothing inherently wrong with having junior engineers conducting interviews. But if a junior engineer is on my interview panel, I'm going to politely decline and end the process. A junior is not going to have the experience to accurately evaluate someone with close to two decades of experience writing software. Same goes for kids with < 10 years of experience who call themselves "senior," which I find happens often at FAANG.

Last I was interviewed by a junior, I brought up a concept for which he had never heard of. Even after explaining it in great detail, he argued with me for half the interview trying to explain why such a system would never hold in practice. Needless to say, I did not get the position. Total waste of my time.